CHARACTERIZATION, ANALYSIS, AND TESTING Flashcards
analytical branch of polymer science
➢Polymer characterization
➢Polymer characterization is a technique used to determine the
molecular properties, structure, and behavior of polymers.
The information obtained from polymer characterization can also be
used for
process control and product quality assessment
Characterization techniques are typically used to
determine
molecular mass
molecular structure
morphology
thermal properties
mechanical properties
Extremely large molecular weights are observed in polymers with
very long chains
The molecular mass of a polymer _______ from typical molecules
differs
t polymerization reactions produce a _________ of molecular
weights and shapes.
distribution
During the polymerization process, ______ polymer chains will grow to
the same length
not all
resulted in the different lengths in the growing part of the polymerization
distribution of chain lengths or
molecular weights.
The distribution of molecular masses can be summarized by
number average molecular weight
weight average molecular weight
polydispersity.
common methods for determining number average molecular weight,
weight average molecular weight and
polydispersity
parameters
colligative property measurements
static light
scattering techniques
viscometry
size exclusion chromatography
There are four molecular weight
averages in common use
number-average molecular weight, Mn
the weight-average molecular weight, Mw
the z-average molecular weight, Mz
viscosity-average molecular weight, Mv
highest to lowest
Mn < Mv < Mw < Mz
equation for Number-Average Molecular Weight, Mn
(image 5 & 6)
Determination of
Molecular Weight (physical and chemical methods)
- end group analysis
- measurement of colligative properties
- light scattering
- Ultracentrifugation
- dilute solution viscosity
- gel permeation chromatography (GPC).
equation of Number-Average Degree of Polymerization, DPn
(image 7)
equation of Weight-Average Molecular Weight
(image 8 &9)
if all species in a polymer sample have the same molecular weight
𝑀𝑛 = 𝑀𝑤 = 𝑀z
If all species in a polymer sample have the same molecular weight (that
is, the polymer is ____________)
monodisperse
ratio Mw/Mn
polydispersity index (PDI)
as a simple measure of the polydispersity of the polymer sample
polydispersity index (PDI)
a chemical method use for calculating the number-average molecular weight of polymer samples whose molecules contain reactive functional groups at one end or both ends of the molecule.
- End-group Analysis
This method is limited to the determination of polymers with a molecular weight of less than about 20,000.
- End-group Analysis
method of analysis in an end-group Analysis
✓Titrimetric method
✓Nuclear magnetic resonance (NMR)
✓mass spectrometry
✓vibrational spectrometry, like infrared and raman spectroscopy.
Limitations/Disadvantages
End-group Analysis
- not applicable to polymers that lack reactive or easily detectable end-groups.
➢not be suitable for polymers with very high molecular weights.
➢problem of selecting a suitable solvent to dissolve the polymer
Properties of solutions that depend on the number of molecules present
and not on the kind of molecules
colligative properties
properties included in colligative properties
boiling point elevation, freezing point depression,
and osmotic pressure.
steps in colligative present
1.beginning with a known mass of solute
2. know the total number of molecules in solution,
- used the knowledge of any of these
colligative properties
3. allows computation of the number-average molecular weight.
Colligative Properties device for Boiling Point Elevation
Ebulliometry
Ebulliometry (Boiling Point Elevation) simple mechanism
boiling point of a
solution of known concentration
vs (compared) solvent at the same pressure.
Boiling point of the solution is _______ than the pure solvent
higher
Boiling point elevation phenomenon is used to determine the
molecular weight of polymers
Colligative Properties device for Freezing Point Depression
Cryoscopy
Calculation of the freezing point depression
calculate freezing-point depression of the
solvent
get molecular weight of the solute
exactly the same way as for
the boiling-point elevation
freezing point depression (mechanism)
- analyzing the melting behavior of a
substance as it is frozen. - By measuring the time it
takes for a specific substance to melt at a certain
temperature - its molecular weight can be calculated.
Like ebulliometry, this is also
limited to relatively low-molecular-weight polymers
with Mn up to ______________
Cryoscopy , 50,000
most important among
all colligative properties for the determination of
molecular weights of
synthetic polymers.
Osmotic pressure
is a technique for the
determination of molecular masses of polymers
by means of osmosis.
Membrane osmometry
describes the attempt of solvent
molecules to go through a semipermeable
membrane into a solution.
The phenomenon of
osmosis
Membrane osmometry is useful to determine
Mn about __________________ and less than __________
20,000-30,000 g/mol and less than
500,000 g/mol
Limitations/Disadvantages of ebulliometry
- time consuming
- sensitive to changes in the
atmospheric pressure - not suitable for use with
volatile substances or highly reactive chemicals due to
the risk of explosion.
Limitations/Disadvantages of ebulliometry
time-consuming (requires a sudden freezing and slow thawing process.
- sensitive to impurities in the monomer solutions (defective polymer formation)
Limitations/Disadvantages of the use of boiling point increase and freezing point lowering is
limited to the determination of the
molecular weights of relatively small polymers
Limitations/Disadvantages of membrane osmometry
- simple but takes
hours to few days in diffusion of solvent through the
semipermeable membrane. - very slow process
and the time taken to attain equilibrium is extremely
high.
-useful in the molecular
weight range of 30,000 to 1,000,00
important
technique for the determination of weight-average molecular weight, Mw
Light- Scattering
Method
absolute method of molecular weight
measurement.
Light- Scattering
Method
LightScattering
Method can furnish information about
- size and shape of polymer molecules in solution
- parameters that characterize the interaction between
solvent and polymer molecules
When polarizable particles are placed in the __________________ of a
beam of light, the light scattering occurs.
oscillating electric field
Light scattering method depends
on the ____
light
when light is passing through polymer solution, it is
measured by _________
lose energy
lose energy happened in Light-Scattering Method
due to the
absorption, conversion to heat and
scattering
The intensity of scattered light relies on the ________________ that is proportionality constant which depends on the
molecular weight
concentration, size
and polarizability
a technique that measures the
intensity of the scattered light to obtain the average
molecular weight Mw of a macromolecule like a polymer or a
protein in solution
Static light scattering
a coherent laser
beam is used to analyze a sample
Static light scattering measurement
The laser beam is
________________ the sample
directed through or passes through
The scattering intensity of the laser beam is measured
at a fixed angle, which is
90°
Light-Scattering Method
limitations and disadvantages
- non-selective and thus requires
purified extracts without co-eluting contaminants to generate
useful data. - Requires a solvent with a different refractive index compared to the solute
✓sensitive to high-molecular-weight species/dust/aggregates. - high price and requires
difficult clarification of the solutions
Light-Scattering Method
advantages
it provides information about macromolecules without any calibration with polymer
standards.
defined as the measure of the opposing force of material to
flow
Viscosity
used to measure viscosity
Viscometry
The average molecular weight
that is measured in viscometry is the
viscosity average molecular weight Mv
The dependence of viscosity on ______ permits estimation of an average
molecular weight from solution viscosity.
size
equation gives the relationship between viscosity and
average molecular weight
Mark-Houwink
Mark-Houwink equation
image 26
most common type of
viscometer that is used for the
determination of viscosity of polymer
solution.
Ubbelohde viscometer
Ubbelohde
viscometer mechanism
- A liquid is introduced into the
reservoir - sucked through the
capillary and measuring bulb. - The liquid is allowed to travel back
through the measuring bulb - the
time it takes for the liquid to pass
through two calibrated marks (start and stop marks) is a
measure for viscosity.
Viscometry
➢Limitations/Disadvantages
- limited to measuring
materials in the liquid or semi-liquid state, (not applicable to
all polymers)
-Viscometry can be affected by the presence of other substances in the
sample (solvents or additives) - more concentrated a polymer solution, the more large molecules you
have exerting drag
The more concentrated a polymer solution,___________________________
the more large molecules you
have exerting drag and interacting with each other.
Higher concentration
leads to a _________________
higher viscosity measurement
extremely powerful method for determining the
complete molecular weight distribution and
average molecular weights
Gel permeation chromatography (GPC)
essentially a
process for the separation of polymer molecules
according to their size.
Gel permeation chromatography (GPC)
Gel permeation chromatography (GPC) MECHANISM
- dilute polymer solution is injected into a solvent stream
- passes through a column packed with
porous gel particles
porosity of porous gel particles
range 50^-10^6 A
known as
gel filtration
gel exclusion chromatography
size-exclusion chromatography (SEC), molecular sieve chromatography
Gel permeation chromatography (GPC)
Gel permeation chromatography (GPC) limitations
- limited number of peaks that can be resolved within the short time scale of the run.
- requires around at least a 10% difference in molecular weight for a
reasonable resolution of peaks to occur. - Filtrations must be performed before using the instrument to prevent dust and other particulates from ruining the columns and interfering with the detectors.
- The molecular masses of most of the chains will be too close for the GPC separation to show anything more than broad peaks.
used to purify and characterize
low-molecular-weight polymers.
Ultracentrifugation
In ______________, both Mw and Mz may be determined by subjecting
dilute solutions of polymers in appropriate solvents to ______________ at high speeds
Ultracentrifugation, ultracentrifugal forces
Solvents with densities and indices of refraction ___________ from the
polymers are chosen to ensure polymer motion and
optical detection of this motion.
different
The ultracentrifuge is operated at __________
speeds up to ____________ in order to transport the
denser polymer molecules through the less dense
solvent to the cell bottom
extremely high , 70,000 rpm
Mw and Mz formula for Ultracentrifugation
(image 31)
Limitations of Ultracentrifugation
Low sample yield
time-consuming process
extremely expensive devices
In preparative ultracentrifugation, samples must be ___________ several
times after spinning, to ensure that there is no cross-contamination between fractions.
washed
Samples for preparative centrifugation are usually ______________ (e.g., tissues) or
_______________ (e.g., cell suspensions or blood).
limited in size , volume
In every wash step that a sample is subjected
to, there is a ___________ , and thus, after an ultracentrifugation protocol, the yield
can be very low.
loss of material
has proved to be a rapid and precise method of molecular-weight
determination, often requiring as little as a half hour per sample.
gel permeation chromatography , GPC
two techniques that are encountered most commonly are
intrinsic
viscosity and gel permeation chromatography , GPC
Many of the analytical techniques used to determine the
____________________________________ are
also used in** polymer characterization**.
molecular structure of unknown organic compounds
_________________________ such as ultraviolet-visible
spectroscopy, infrared spectroscopy, Raman
spectroscopy, nuclear magnetic resonance spectroscopy,
electron spin resonance spectroscopy, X-ray diffraction,
and mass spectrometry are used to identify common
functional groups.
Spectroscopic techniques
Spectroscopic techniques such as ultraviolet-visible
spectroscopy, infrared spectroscopy, Raman
spectroscopy, nuclear magnetic resonance spectroscopy,
electron spin resonance spectroscopy, X-ray diffraction,
and mass spectrometry are used to identify common ______________
functional groups.
microscale property that is
largely dictated by the** amorphous or crystalline portions **
of the polymer chains and their influence on each other
Polymer morphology
are especially useful in
determining these microscale properties, as the
domains created by the polymer morphology are large
enough to be viewed using modern microscopy
instruments.
Microscopy techniques
➢Some of the most common microscopy techniques used
are
X-ray diffraction
Transmission Electron Microscopy
Scanning Transmission Electron Microscopy
Scanning Electron Microscopy
Atomic Force Microscopy
ANALYSIS AND
TESTING
A. CHEMICAL ANALYSIS OF POLYMERS
B. SPECTROSCOPIC METHODS
C. X-RAY DIFFRACTION ANALYSIS
D. MICROSCOPY
E. THERMAL ANALYSIS
F. PHYSICAL TESTING
MECHANICAL
PROPERTIES
a. Stress-Strain Properties in Tension
b. Fatigue Tests
c. Impact Tests
d. Tear Resistance
e. Hardness
f. Abrasion Resistance
THERMAL
PROPERTIES
a. Softening Temperature
b. Flammability
OPTICAL
PROPERTIES
a. Transmittance and Reflectance
b. Color
c. Gloss
d. Haze
e. Transparency
ELECTRICAL
PROPERTIES
a. Resistivity
b. Dielectric Constant
c. Dielectric Strength
d. Arc Resistance
CHEMICAL
PROPERTIES
a. Resistance to Solvents
b. Vapor Permeability
c. Weathering
polymer is allowed to react to form low-molecular-weight fragments that are
condensed at liquid-air temperature
Mass
Spectrometry
volatilized, ionized and separated
according to mass and charge by the
action of electric and magnetic fields
Mass
Spectrometry
Mass spectrometry, from the abundance of the various ________found, the ________________ of the low molecular weight species can be inferred.
ionic species, structures
example of Mass
Spectrometry
Matrix-Assisted Laser
Desorption/Ionization
(MALDI)
is an ionization technique that uses a **laser energy-absorbing matrix **to create ions from large molecules with minimal
fragmentation
matrix-assisted laser
desorption/ionization (MALDI)
can be used to
determine the molar mass distribution
matrix-assisted laser
desorption/ionization (MALDI)
Mass Spectrometry Strength
1.Compound Identification -accurate based on their mass spectra, allowing the detection of unknown or trace compounds.
2.**High Sensitivity and Specificity **-enabling detection of compounds at very low concentrations, and high specificity due to the unique mass spectra of different compounds.
3.Quantitative Analysis-accurate quantification of compounds based on ion abundance
Mass Spectrometry Limitations
1.Sample Preparation: Samples must be compatible with the ionization method
2.Complexity and Cost: Mass spectrometers expensive to purchase, maintain, and operate. Specialized expertise is required for
method development and data interpretation.
3.Instrument Sensitivity: presence of contaminants or interfering compounds
method of separation in
which gaseous or vaporized components are
distributed between a moving gas phase and fixed
liquid phase or solid adsorbent
Gas
Chromatography
Gas
Chromatography step by step
- adsorption, separation is achieved.
- components are detected as they emerge from the chromatographic column
- From the detector signal, number, nature, and amounts of the components present.
analytical technique used to separate the
chemical components of a sample mixture and then detect them to determine their presence or absence.
Gas
Chromatography
It is also used to figure out** how much is present** in
the sample.
Gas
Chromatography
analytical method that combines the features
of gas-chromatography and mass spectrometry to
identify different substances within a test sample.
Gas
chromatography–
mass spectrometry
combines the separation capabilities of gas
chromatography with the identification and
quantification abilities of mass spectrometry
Gas
chromatography–
mass spectrometry
can provide detailed information about the
molecular structure and composition of polymers,
including their monomer sites, stereochemistry, and
branching patterns.
Gas
chromatography–
mass spectrometry
Gas Chromatography
Strengths
1. High Separation Efficiency: Allows the separation of complex mixtures into individual components, even for compounds present in trace amounts.
2. Quantitative Analysis: Provides accurate quantification of compounds through calibration curves or peak area integration in the chromatogram.
3. Wide Range of Applications: Applicable to a diverse range of sample types and compounds, offering versatility in analytical tasks
Gas Chromatography Limitations
1. Limited Volatility: Compounds need to be volatile or semi-volatile to be efficiently separated and
detected by GC.
2. Thermal Stability: Some compounds may decompose or react within the high-temperature
environment of the GC column, affecting their separation and detection.
3. Sample Preparation: Sample preparation steps, such as extraction and derivatization, might be
required, adding complexity to the analysis
analysis
of infrared light interacting with a
molecule
Infrared
Spectroscopy
can be analyzed in
three ways by measuring absorption,
emission and reflection.
Infrared
Spectroscopy
ways to measure Infrared
Spectroscopy
absorption,
emission and reflection.
measures the
vibrations of atoms
Infrared
Spectroscopy
to determine the
functional groups
measures the
vibrations of atoms
non-destructive analytical technique that
measures the** absorption or transmission **of
infrared radiation by a sample as a function of
frequency or wavelength
Fourier transform
infrared
spectroscopy (FTIR)
reliable and cost-effective analytical tool
for identification of polymers and assessment
of the quality of plastic materials
Fourier transform
infrared
spectroscopy (FTIR)
In Fourier transform infrared spectroscopy (FTIR), when a plastic material absorbs infrared light, typically in the mid-infrared region, the resulting spectrum (absorbance or transmittance) gives a distinctive _____________ that can be used to
easily screen and test samples for many
different applications.
“fingerprint”
Fourier transform infrared spectroscopy
(FTIR)
Strengths
◦ high sensitivity, specificity, and ability to provide a wealth of information about the chemical composition and structure
◦ can detect very small amounts in complex mixtures and can provide quantitative
data.
◦ relatively simple and rapid technique that can analyze solid, liquid, and gas samples.
Fourier transform infrared spectroscopy
(FTIR)
Limitations
- inability to provide three-dimensional
structure of a molecule and its **sensitivity **to interference from water and other atmospheric gases.
◦ pone to interference from sample preparation artifacts, such as **impurities or
contaminants. **
◦ **expensive technique **that requires specialized training and expertise to interpret
the spectra correctly.
powerful analytical technique used to study the **molecular structure, dynamics, and composition of organic and inorganic ** compounds
Nuclear Magnetic Resonance
(NMR) spectroscopy
Nuclear Magnetic Resonance (NMR) spectroscopy
Strengths
Structural Information: detailed molecular structures, including bond connectivity,
stereochemistry, and molecular dynamics.
Non-Destructive and Non-Invasive: allows repeated measurements without altering the sample.
Quantitative Analysis: quantifying the abundance of different nuclei within a sample.
Versatility: wide range of compounds, including organic and inorganic molecules, solids, liquids, and
gases.
It exploits the magnetic properties of certain atomic nuclei within a magnetic field to provide detailed information about the chemical environment of atoms in a molecule
Nuclear Magnetic Resonance (NMR) spectroscopy
In Nuclear Magnetic Resonance (NMR) spectroscopy, _________ with an odd number of protons or neutrons
possess a _____________ and a magnetic moment, which allows
them to absorb and emit electromagnetic radiation at specific
frequencies
Atomic nuclei , nuclear spin
Nuclear Magnetic Resonance (NMR) spectroscopy
Limitation
Sensitivity: limited in sensitivity, requiring large sample and limits trace analysis.
Instrument Cost and Complexity: expensive to purchase and maintain
Sample Requirements: Samples must be pure and relatively concentrated, and sample preparation can be timeconsuming.
Complex Spectral Interpretation: Interpreting NMR spectra might be challenging, especially for complex molecules
detection of free radicals
Electron Paramagnetic
Resonance Spectroscopy
uniquely characterized by their magnetic moment, arising from the presence of an unpaired electron.
free radicals
EPR works by measuring the presence of __________ or molecules with unpaired electrons, and by observing the____________ of microwaves within a static magnetic field.
paramagnetic ions , resonant absorption
can be used to study radical reactions in polymers
Electron Paramagnetic
Resonance Spectroscopy
non-invasive and
non-destructive magnetic resonance technique, therefore perfect for detecting paramagnetic species like free radicals, bi-radicals, transition metal ions, triplet state systems, and point defects.
Electron Paramagnetic
Resonance Spectroscopy
Electron Paramagnetic
Resonance
Spectroscopy
Strengths
◦ Sensitivity to Unpaired Electrons: making it suitable for studying free radicals and
paramagnetic species present in trace
amounts.
◦ Non-Destructive and Non-Invasive: doesn’t require extensive sample preparation, allowing for repeated measurements on the same sample.
◦ Information about Molecular Structure and
Environment: information about
the electronic structure, coordination
environment, and dynamics of paramagnetic
species
valuable technique for analyzing
polymers, providing insights into their electronic structure,
composition, and molecular interactions.
Ultraviolet–visible
spectroscopy
used to study the
**absorption of ultraviolet and visible light **by polymer
molecules
Ultraviolet–visible
spectroscopy
Ultraviolet–visible
spectroscopy steps
- light source
- wavelength selector (inlet: light)
- sample (inlet: light)
- detector (inlet: light)
- computer for singe processing and output (inlet: electric current)
Ultraviolet–visible
spectroscopy principle
Electronic Transitions
Polymers exhibit electronic transitions in the UV and visible regions due to the presence of _____________. These
transitions involve movement of electrons between energy levels, leading to absorption
of specific wavelengths of light
conjugated double bonds or chromophores
Applications of Ultraviolet–visible
spectroscopy
Polymer Characterization - functional groups, analyzing the presence of chromophores or additives.
Quality Control - purity and composition
Polymer Processing - degradation or changes
Ultraviolet–
visible
spectroscopy Strengths
Qualitative Analysis: information about the
presence of specific functional groups or chromophores within polymers.
**Rapid Analysis: **Quick measurements enable efficient screening of samples.
**Non-destructive: **Allows for the analysis of polymer
samples without altering their structure.
Ultraviolet–
visible
spectroscopy
Limitations
**Quantitative Analysis Challenges: **due to the complex nature of
polymer mixtures and overlapping absorption bands.
Sensitivity: Limited sensitivity for trace-level analysis of polymers compared to other techniques.
Sample State: Limited to solutions or transparent solid forms, which might not represent the polymer’s actual structure in its intended application
powerful **qualitative and
quantitative tool **with some particular advantages for the
analysis of polymers.
Raman spectroscopy
an analytical technique used to
study molecular vibrations in materials by measuring the
scattering of light when it interacts with a sample
Raman spectroscopy
provides information about molecular structure, chemical
composition, and bonding within a sample based on the
vibrational modes of its constituent molecules
Raman spectroscopy
Raman spectroscopy
Principle:
- a laser beam is directed onto a
sample - small fraction of the incident light
undergoes inelastic scattering. - The scattered light exhibits energy shifts corresponding to the **vibrational energy levels **of the molecules in the sample.
- The resulting spectrum provides
information about molecular vibrations, allowing identification of** functional groups** and chemical bonds present
Raman spectroscopy
➢Strengths
1.Chemical Specificity: detailed information
about chemical composition, including molecular
structures, functional groups, and bonding
configurations.**
2.Non-Destructive and Non-Invasive:
requires minimal to no sample preparation, and it
can analyze samples in situ.
**3.Versatility: **wide range of materials,
including solids, liquids, gases, and biological
samples.
4.High Spatial Resolution: With modern
instrumentation, Raman spectroscopy can achieve
high spatial resolution, enabling microscopic
analysis at the sub-micron level.
Raman spectroscopy
➢Limitations
1.Fluorescence Interference:
can interfere with Raman signals, reducing the
signal-to-noise ratio and complicating spectral
interpretation.
2.Low Sensitivity: requiring longer acquisition times or high laser power for some samples, which might cause sample damage.
3.Water and Background Interference: Water and other background signals may overlap with Raman bands, affecting accuracy in aqueous or complex samples.
4.Instrumentation Complexity and Cost: Highperformance Raman spectrometers can be
expensive, and interpreting complex spectra may
require expertise
nondestructive technique that provides detailed information about the crystallographic structure, chemical composition, and physical properties of a material
X-Ray diffraction analysis (XRD)
has become the go-to tool for
identifying the type and crystallinity of polymer materials
X-ray diffraction (XRD)
X-ray diffraction analysis works by passing X-rays through** a sample** and analyzing the ____________ produced by the scattering of X-rays by the polymer molecules.
diffraction pattern
X-ray diffraction analysis technique provides information about the _______________________________ of the polymer.
chain length, flexibility, and degree of order
X-ray diffraction analysis
Strengths
◦ Least expensive and most convenient.
◦ Widely used method to determine crystal structures.
◦ The best method for phase analysis.
◦ X-rays are not absorbed very much by air, so the sample need not be in an evacuated chamber.
X-ray diffraction analysis
Limitations
X-rays do not interact very strongly with lighter
elements
category of microscopes
that uses visible light to
magnify and image small
samples.
Light
Microscopy
valuable for examining the
texture of solid opaque
polymers
Light Microscopy
technique used to observe the
orientation of molecules in a sample under a microscope.
Polarized-light
Microscopy
It is often used with polymers to study their structure, as the orientation of the polymer chains can reveal information about
their molecular organization.
Polarized-light
Microscopy
is a type of
microscopy that uses interference patterns
produced by the incoherent light scattered by specimens to create an image.
Phase-contrast
Microscopy
commonly used in materials science and
polymer science to **observe changes in the
morphology **of polymers during phase
transitions or in response to external stimuli
Phase-contrast
Microscopy
can provide valuable information about the structure and behavior of polymers at the micrometer scale, such as domain size, chain
organization, and interface properties
Phase-contrast
Microscopy
powerful tool in the
study of the morphology of crystalline polymers
Electron
Microscopy
uses a beam of
electrons and their wave-like characteristics to
magnify an object’s image, unlike the optical
microscope that uses visible light to magnify
images
Electron
Microscopy
a microscope that
uses a beam of electrons as a source of
illumination
Electron
Microscopy
Electron Microscopy use _ that are
_ to the glass lenses of an optical light
microscope** to control the electron beam**, for instance focusing them to produce magnified
images or electron diffraction patterns.
electron optics , analogous
type of electron microscope that produces
images of a sample by** scanning the surface **
with a focused beam of electrons.
Scanning Electron
Microscope (SEM)
Under this, the electrons interact with atoms in the sample, producing various signals that contain
information about the** surface topography **
and composition of the sample
Scanning Electron
Microscope (SEM)
type of electron microscope that transmits
electrons through a** thin sample**, resulting in an image of the sample’s interior structure at the atomic level
Transmission
Electron
Microscopy
(TEM)
analytical technique used to visualize the
smallest structures in matter
Transmission
Electron
Microscopy
(TEM)
Unlike optical microscopes, which rely on light in the visible spectrum, Transmission Electron Microscopy (TEM) can reveal stunning detail at
the atomic scale by magnifying nanometer
structures up to ______________
50 million times
thermoanalytical technique in which the difference in the **amount of heat required **to increase the
temperature of a sample and reference is measured as a function of temperature.
. Differential
Scanning
Calorimetry
used widely for examining polymeric materials
to determine their thermal transitions. Important thermal transitions include the glass transition temperature (Tg), crystallization temperature (Tc), and melting temperature (Tm). The observed thermal
transitions can be utilized to compare materials.*
. Differential
Scanning
Calorimetry
the material under study and an inert reference are made to undergo identical thermal cycles, (i.e., same cooling or heating programme) while recording any temperature difference between sample and reference
Differential
Thermal Analysis
Changes in the sample, either
exothermic or endothermic, can be detected relative to the inert reference
Differential
Thermal Analysis
This differential temperature is then plotted
against time, or against temperature (DTA curve, or
________________).
thermogram
Curve that provides data on
the transformations that have occurred, such as glass transitions, crystallization, melting and sublimation.
DTA curve
a sensitive balance is used to follow the
weight change of the sample as a function of
temperature
Thermogravimetric
Analysis
Typical applications include the
**assessment of thermal stability **and
decomposition temperature, extent of cure in condensation polymers, composition and some information on sequence distribution in copolymers, and composition of filled polymers,
among many others
Thermogravimetric
Analysis
measures the mechanical
response of a polymer system
as the temperature is changed.
Thermomechanical
Analysis
Typical measurements include
dilatometry, penetration or
heat deflection, torsion
modulus, and stress-strain
behavior
Thermomechanical
Analysis
image 77
stress-strain curve showing elastic and plastic region
One of the most informative
mechanical experiments for
any material is the
determination of its stressstrain curve in tension.
Stress-Strain
Properties in
Tension
done by measuring
continuously the force
developed as the sample is
elongated at constant rate of
extension
Stress-Strain
Properties in
Tension
maximum
stress that a material can withstand
while being stretched or pulled
before breaking.
Tensile strength
material property
and is the stress corresponding to
the yield point at which the material
begins to** deform plastically**
Yield strength
mechanical property of solid
materials that measures the tensile
or compressive stiffness when the
force is applied lengthwise.
Young’s modulus (or Young modulus)
measure of the stress or force that is applied in a direction **parallel to the surface **
of a material.
Shear stress
It is typically defined as the force per unit area perpendicular to the plane of shearing
force.
Shear stress
refers to the bending or storage of stress or strain in a material.
Flexure
It is a mechanical
phenomenon that occurs when force is applied to a flexible material.
Flexure
In flexure, the amount of bending that
occurs depends on the material’s properties, such as its ___________ and _______________
modulus of elasticity , cross-sectional
area
is the twisting of an object due to an applied torque.
Torsion
the force that is responsible for the deformation of the material such that the
volume of the material reduces.
Compressive stress
High compressive stress leads to ____________ of the material due to tension.
failure
image 80
- soft and weak
- hard and brittle
- soft and tough
- hard and strong
- hard and tough
Based on Stress-Strain Curve Soft, weak polymer
modulus: low
yield strength: low
ultimate strength: low
elongation at break: ,moderate
Based on Stress-Strain Curve Soft, tough polymer
modulus: low
yield strength: low
ultimate strength: yield stress
elongation at break: high
Based on Stress-Strain Curve hard, brittle polymer
modulus: high
yield strength: none
ultimate strength: moderate
elongation at break: low
Based on Stress-Strain Curve hard, strong polymer
modulus: high
yield strength: high
ultimate strength: high
elongation at break: moderate
Based on Stress-Strain Curve hard, tough polymer
modulus: high
yield strength: high
ultimate strength: high
elongation at break: high
When subjected to **cyclic mechanical **
stresses, most materials fail at a stress
considerably lower than that required to
cause rupture in a single stress cycle.
fatigue
performed to measure the
reduction in stiffness and strength of
materials under repeated loading and to
determine the total number of load cycles to
failure.
Fatigue Tests
Various modes of fatigue testing in common
use include
alternating tensile
compressive stress
cyclic flexural stress
measure the ability of a
material to resist deformation in response
to a sudden load
Impact Tests
Four commonly used types of impact tests
include
Charpy, Izod, drop-weight, and
dynamic tear tests
The benefits of conducting impact testing
on materials include
- to determine a material’s toughness
- establishing quality control standards
- optimizing designs
- picking appropriate materials for particular applications.
occurs if the material behaves elastically up to the point of failure
Brittle rupture
occurs when the specimen is permanently distorted near the point of failure.
Ductile rupture
The brittle point, or temperature at the onset of brittleness, is usually determined by subjecting a specimen to _____________________
impact in a standardized but empirical way.
commonly measured by tests in which a
pendulum with a massive striking edge is allowed to hit the specimen. From the
travel of the pendulum after breaking the specimen can be calculated the energy required to cause the break
Impact strength
When plastics are used as films,
particularly in packaging applications,
their _______________ is an
important property.
resistance to tearing
a specimen is torn apart at a cut made
by a sharp blade. Energy is provided
by a falling pendulum, and the work
done is measured by the residual
energy of the pendulum
tear strength
composite property
combining concepts of resistance to
penetration, scratching, marring, and
so on
Hardness
crucial characteristic that governs a material’s
resistance to abrasion, scratching, and
other types of mechanical deformation
Polymer hardness
It is an important consideration for
choosing and designing polymers for a
range of applications, including
technical parts, consumer goods, and
biomedical equipment
Hardness
takes the form of a scratch test, in which
the material is subjected to many
scratches, usually from contact with an
abrasive wheel or a stream of falling
abrasive material
Abrasion
Resistance
defined as the
temperature at which the resin flows under a
given load on heating
Softening
Temperature
In measuring softening temperature
1) A polymer sample becomes molten and
leaves a trail when moved across a ______________with moderate pressure
(polymer melt or stick temperature tests;
hot
metal surface
In measuring softening temperature
2) A polymer specimen fails in tension under
its own weight
(zero-strength temperature
test).
usually tested
as the burning rate of a specified
sample
Flammability
___________________
tendency of the material on the
removal of an external flame is
also important
self-extinguishing
A major determinant of the appearance of a transparent material is its
_____________________
transmittance
the ratio of the intensities of light passing through and light incident on the specimen
transmittance
The appearance of an opaque material is characterized by its ______________
reflectance
the ratio of the intensities of the reflected and the incident light
reflectance
A _____________ substance is one that transmit part and reflects part of the light incident on it
translucent
______________________ and _____________________ may be measured as a function of the
wavelength of light in a spectrophotometer
Transmittance and reflectance
is the subjective sensation in
the brain resulting from the
perception of those aspects of the
appearance of objects that result
from the spectral composition of the
light reaching the eye.
Color
In commercial hazemeters only
light deviating more than _____________
from the transmitted beam
direction is considered haze.
2.5 degree
The effect of __________ is to impart a
cloudy or milky appearance to the
sample
haze
_____________ is defined as the state **permitting perception of objects **through or
beyond the specimen.
Transparency
of polymers refers to their** degree of clarity or opacity,** or how much
they allow light to pass through them
Transparency
Polymers can be made transparent by ________________________ their
chemical structure, resulting in materials with varied levels of transparency.
incorporating additives or modifying
The transparency of polymers has numerous applications in industries such as
__________________, where clarity is necessary for specific
purposes.
packaging, textiles, and electronics
refers to the ability of a polymer material to resist the flow of electrical current.
Resistivity
important property of polymers used in electronic applications, such as in
the production of **interconnected circuit components, conductive films, and
insulators. **
Resistivity
The resistivity of polymers can be modified through the ___________________________ through crosslinking or chain modification.
addition of conductive
insulating fillers
by altering the polymer structure
The value of the resistivity depends on factors such as the
type and concentration of the polymer
the crosslink density
the presence of defects
Both _______ and _____________ resistivity are important properties for applications of
polymers as insulating materials.
volumesurface , volume
a measure of a
material’s ability to store electric charge.
Dielectric
Constant
influenced by factors such as the
type and structure of the polymer, as well as
the presence of any** additional groups.**
Dielectric
Constant
why Dielectric
Constant needs to consider sa design?
it can affect performance and
reliability
measure of its ability to sustain high-voltage
differences without current breakdown.
Dielectric
Strength
measure of the
electrical strength of a material as an insulator
Dielectric
Strength
affected by factors such as the type of polymer,
its molecular structure, and the **presence of impurities. **
Dielectric
Strength
________ dielectric strengths are typically
desirable in capacitors
Higher
The surfaces of some polymers may become ______ and conduct current readily when exposed to an electrical discharge.
carbonized
ability of the plastic material to resist
the action of a high voltage electrical arc and resist the formation of a conducting path along its surface under a given time.
Arc resistance
This property is important in applications such as
hightemperature dielectrics
coatings
insulation materials.
Polymer materials are chosen for their high arc resistance due to their ability to withstand ____________ and protect against _____________
high temperatures , electrical arcs
several forms of effects of solvents
solubility
swelling including the absorption of water
specimen fails by **breaking when exposed to
mechanical stress **in the presence of an organic liquid of an aqueous solution of a soap or other wetting agent
environmental stress
cracking
specimen fails by the development of a multitude of very small cracks in the presence of an organic liquid or its vapor, with or without the
presence of mechanical stress.
crazing
When polymers are exposed to solvents, they may become _____________ depending on the type of polymer and solvent
swollen or dissolved
The resistance of polymers to solvents can be influenced by factors such as
the
polymer’s structure
solvent’s strength
temperature.
Polymers that are resistant to solvents are often used in applications where _______ and ________ are required, such as in clothing, tires,
and electronics
strength , durability
**product of the solubility **of the gas or vapor
in the polymer and its diffusion coefficient
permeability of a polymer to a gas or vapor
directly measured as the rate of transfer of vapor through unit thickness of the
polymer in film form, per unit area and pressure difference across the film.
(KT/AP)
Permeability
refers to the ability of a polymer material to allow certain gases or vapors to
pass through it.
Vapor permeability
The vapor permeability of polymers can be influenced by factors such as the
molecular weight
structure
composition of the polymer
presence of additives
temperature
humidity conditions
refers to the process of
degradation of polymers, or large molecules, due to
exposure to external factors such as sunlight,
temperature, and chemicals.
Weathering
this can cause the polymer material to break
down into smaller fragments, leading to changes in its physical and chemical properties.
Weathering
can have a significant impact on the
performance and lifespan of polymer-based products,
such as plastics, coatings, and rubber
Weathering
